Method for extracting lithium carbonate from lithium slag by wet process and application of residual lithium slag

Abstract

The invention discloses a method for extracting lithium carbonate from lithium slag through a wet method and application of residual lithium slag, and belongs to the technical field of metal smelting. In the initial stage of preparing artificial sand through the lithium slag wet method, a trace amount of a water reducing agent is added in an acid environment to promote lithium ions to be dissociated from a slag phase, lithium loss is reduced, and the recovery efficiency is improved; and collecting a solution obtained by circulating filter pressing and water washing of the lithium slag, adding sodium carbonate to remove calcium and sodium hydroxide to neutralize, and filtering, removing impurities and concentrating to obtain lithium carbonate filtrate, so that coprecipitation of calcium impurities and lithium is avoided, the lithium ion enrichment concentration of the filtrate is ensured to reach 2.5-5g / L, and the lithium carbonate filtrate can be directly used for purifying lithium carbonate. In addition, the dehydrated lithium slag is directly used for preparing the artificial sand, so that zero emission of solid waste is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal smelting, and particularly relates to a method for extracting lithium carbonate from lithium slag by a wet process and application of residual lithium slag. BACKGROUND

[0003] At present, lithium slag can be prepared into artificial sand by a dry process or a wet process. In the initial stage of the wet process, the lithium slag needs to be subjected to multiple cycles of pressure filtration and water washing, and a large amount of lithium atoms are lost in the water washing process, resulting in low recycling rate of the lithium slag. In addition, the lithium slag contains part of high-value elements such as potassium, lithium, rubidium, cesium and beryllium in the form of mineral association. Therefore, how to utilize the different forms and properties of the elements and select a suitable process to separate and purify the target elements is an effective way to improve the resource value of the waste slag. SUMMARY

[0004] In order to solve the technical problem that in the wet process for preparing artificial sand from lithium slag, multiple cycles of pressure filtration and water washing in the initial stage result in a large amount of lithium atom loss and low recycling rate of the lithium slag, the application provides a method for extracting lithium carbonate from lithium slag by a wet process and application of residual lithium slag. The water in the pressure filtration cycle is recovered and treated to obtain lithium carbonate with high purity, which can be sent to a lithium carbonate plant for re-extraction of lithium and other valuable elements, and the residual lithium slag can also be applied in subsequent preparation of artificial sand. To achieve the above purpose, the technical scheme of the application is as follows.

[0005] A method for extracting lithium carbonate from lithium slag by a wet process, comprising the following steps:

[0006] Step one, crushing the lithium slag;

[0007] Step two, adding a water reducing agent and water to the crushed lithium slag for ball milling;

[0008] Step three, performing cyclic pressure filtration dewatering on the ball-milled lithium slag;

[0009] Step four, collecting the solution after the cycle and the residual lithium slag after dewatering;

[0010] Step five, adding sodium carbonate and sodium hydroxide to the collected solution and performing filtration to remove impurities, and concentrating the filtrate after filtration to obtain a lithium carbonate filtrate.

[0011] Preferably, the water reducing agent added to the lithium slag in the step two is a solid polycarboxylic acid type water reducing agent, and the mass percentage of the water reducing agent accounts for 0.3-0.5% of the lithium slag. The addition of the water reducing agent is beneficial to the separation of lithium ions from the surface of the lithium slag into the solution.

[0012] Preferably, the PH value of the water added to the lithium slag in the step two is 2-5, and the ball milling is performed at 10-40℃ for 3-5 min.

[0013] Preferably, the concentration of sodium carbonate added in step five is 5%, and the mass percentage is 3% to 10%; the concentration of sodium hydroxide added is 5%, and the mass percentage is 1% to 3%. The sodium carbonate is used to remove calcium ions in the solution to avoid the precipitation of lithium ions; and the sodium hydroxide is used to neutralize the solution to neutral.

[0014] Preferably, in step five, the filtrate after impurity removal is concentrated to a lithium ion concentration of 2.5 to 5 g / L to obtain a lithium-rich filtrate, which can be sent to a lithium carbonate plant for further extraction of lithium elements and other valuable elements.

[0015] Preferably, the filtration and impurity removal uses a filter plate or filter membrane with a pore size of 0.02 to 2 µm.

[0016] Preferably, in step one, the lithium residue is derived from lithium mica and / or lithium spodumene production, and the density of the lithium residue is 1.0 to 1.2 g / cm 3 , and the specific surface area is 80 to 200 m 2 / kg.

[0017] Preferably, when the lithium residue is derived from lithium mica, the lithium residue needs to be crushed to 200 to 400 mesh.

[0018] Preferably, in step three, the pressure filtration dewatering is cycled 5 to 10 times. Through multiple cycles of water washing, lithium ions are maximally extracted, and the water consumption is controlled to avoid excessive dilution of the solution.

[0019] The application also provides the use of the remaining lithium residue after dewatering in the preparation of artificial sand. The dewatered lithium residue is directly used to prepare artificial sand, achieving zero discharge of solid waste.

[0020] Compared with the prior art, the application has the following beneficial effects:

[0021] By adding a small amount of water reducing agent in the initial stage of preparing artificial sand from lithium residue by a wet method, the dissolution of lithium ions from the residue phase is promoted in an acidic environment, lithium loss is reduced, and the recovery efficiency is improved; the solution collected from the cyclic pressure filtration and water washing of the lithium residue is added with sodium carbonate to remove calcium and sodium hydroxide to neutralize, filtered and impurity-removed, and concentrated to obtain a lithium carbonate filtrate, which avoids the co-precipitation of calcium impurities and lithium, ensures that the lithium ion enrichment concentration of the filtrate reaches 2.5 to 5 g / L, and can be directly used for lithium carbonate purification. In addition, the dewatered lithium residue is directly used to prepare artificial sand, achieving zero discharge of solid waste. DETAILED DESCRIPTION

[0022] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present application.

[0023] The present embodiment provides a method for extracting lithium carbonate from lithium slag by wet method and application of residual lithium slag. In the initial stage of preparing artificial sand from lithium slag by wet method, a small amount of water reducing agent is added in an acidic environment to promote the dissociation of lithium ions from the slag phase, reduce lithium loss, and improve recovery efficiency. The solution collected by recycling pressure filtration and water washing of lithium slag is added with sodium carbonate to remove calcium and sodium hydroxide for neutralization, filtration, impurity removal and concentration. The obtained lithium carbonate filtrate can be directly used for lithium carbonate purification, and the dehydrated lithium slag can be directly used for preparing artificial sand, realizing zero discharge of solid waste. The specific implementation is as follows:

[0024] A method for extracting lithium carbonate from lithium slag by wet method, comprising the following steps:

[0025] Step one, crushing the lithium slag;

[0026] Step two, adding water reducing agent and water to the crushed lithium slag for ball milling;

[0027] Step three, dehydrating the ball-milled lithium slag by recycling pressure filtration;

[0028] Step four, collecting the solution after recycling and the residual lithium slag after dehydration;

[0029] Step five, adding sodium carbonate and sodium hydroxide to the collected solution, and filtering out impurities. The filtrate after filtration is concentrated to obtain a lithium carbonate filtrate.

[0030] As a preferred embodiment, the water reducing agent added to the lithium slag in step two is a solid polycarboxylic acid type water reducing agent, with a mass percentage of 0.3-0.5% of the lithium slag. Adding water reducing agent is beneficial to the separation of lithium ions from the surface of the lithium slag into the solution.

[0031] As a preferred embodiment, the pH value of the water added to the lithium slag in step two is 2-5, and the ball milling is carried out at 10-40℃ for 3-5min.

[0032] As a preferred embodiment, the concentration of sodium carbonate added in step five is 5%, with a mass percentage of 3-10%; the concentration of sodium hydroxide added is 5%, with a mass percentage of 1-3%. The sodium carbonate is used to remove calcium ions in the solution to prevent precipitation of lithium ions; the sodium hydroxide is used to neutralize the solution to neutral.

[0033] As a preferred embodiment, the filtrate after impurity removal in step five is concentrated to a lithium ion concentration of 2.5-5 g / L, i.e. a lithium-rich filtrate, which can be sent to a lithium carbonate plant for further extraction of lithium elements and other valuable elements.

[0034] As a preferred embodiment, the filtration and impurity removal uses a filter plate or filter membrane with a pore size of 0.02-2 µm.

[0035] As a preferred embodiment, the lithium residue in step one is derived from lithium mica and / or spodumene production, and the density of the lithium residue is 1.0-1.2 g / cm 3 , and the specific surface area is 80-200 m 2 / kg.

[0036] As a preferred embodiment, when the lithium residue is derived from lithium mica, the lithium residue needs to be crushed to 200-400 mesh.

[0037] As a preferred embodiment, the pressure filtration and dewatering in step three is cycled 5-10 times. Through multiple water washing cycles, lithium ions are maximally extracted, while water consumption is controlled to avoid excessive dilution of the solution.

[0038] The application also provides the use of the remaining lithium residue after dewatering in the preparation of artificial sand. The dewatered lithium residue is directly used to prepare artificial sand, achieving zero discharge of solid waste.

[0039] The application will be further described in detail below in conjunction with specific examples:

[0040] Example 1

[0041] The present embodiment provides a method for extracting lithium carbonate from lithium residue, comprising the following steps:

[0042] Step one: crushing the lithium residue to 200-400 mesh;

[0043] Step two: adding a water reducing agent accounting for 0.3% of the mass percentage of the lithium residue to the crushed lithium residue, and ball milling in a water solvent with a pH of 2, at a temperature of 10°C;

[0044] Step three: performing pressure filtration and dewatering of the ball-milled lithium residue for 5 cycles;

[0045] Step four: collecting the solution after the cycles and the remaining lithium residue after dewatering;

[0046] Step five: adding sodium carbonate and sodium hydroxide to the collected solution, and performing filtration and impurity removal, and concentrating the filtrate to obtain a lithium carbonate filtrate.

[0047] Example 2

[0048] The embodiment provides a method for extracting lithium carbonate from lithium residue, and comprises the following steps.

[0049] Step one, crushing the lithium residue to 200-400 mesh;

[0050] Step two, adding water reducing agent accounting for 0.4% of the mass percentage of the lithium residue to the crushed lithium residue, and performing ball milling in a water solvent with a pH value of 3, and the temperature is 20 DEG C;

[0051] Step three, performing pressure filtration and dehydration cycle for the ball-milled lithium residue for 6 times;

[0052] Step four, collecting the solution after the cycle and the residual lithium residue after dehydration;

[0053] Step five, adding sodium carbonate and sodium hydroxide to the collected solution, and performing filtration to remove impurities, and concentrating the filtrate after filtration, so as to obtain lithium carbonate filtrate.

[0054] Embodiment 3

[0055] The embodiment provides a method for extracting lithium carbonate from lithium residue, and comprises the following steps:

[0056] Step one, crushing the lithium residue to 200-400 mesh;

[0057] Step two, adding water reducing agent accounting for 0.5% of the mass percentage of the lithium residue to the crushed lithium residue, and performing ball milling in a water solvent with a pH value of 4, and the temperature is 30 DEG C;

[0058] Step three, performing pressure filtration and dehydration cycle for the ball-milled lithium residue for 8 times;

[0059] Step four, collecting the solution after the cycle and the residual lithium residue after dehydration;

[0060] Step five, adding sodium carbonate and sodium hydroxide to the collected solution, and performing filtration to remove impurities, and concentrating the filtrate after filtration, so as to obtain lithium carbonate filtrate.

[0061] Embodiment 4

[0062] The embodiment provides a method for extracting lithium carbonate from lithium residue, and comprises the following steps:

[0063] Step one, crushing the lithium residue to 200-400 mesh;

[0064] Step two, adding water reducing agent accounting for 0.4% of the mass percentage of the lithium residue to the crushed lithium residue, and performing ball milling in a water solvent with a pH value of 5, and the temperature is 40 DEG C;

[0065] Step three, performing pressure filtration and dehydration cycle for the ball-milled lithium residue for 9 times;

[0066] Step four, collect the solution after circulation, and the remaining lithium residue after dehydration;

[0067] Step five, add the collected solution to sodium carbonate and sodium hydroxide, and filter out impurities, and concentrate the filtrate after filtration, to obtain a lithium carbonate filtrate.

[0068] Example 5

[0069] The embodiment provides a method for extracting lithium carbonate from lithium residue, comprising the following steps:

[0070] Step one, crush the lithium residue to 200-400 mesh;

[0071] Step two, add 0.4% water reducing agent to the crushed lithium residue, and perform ball milling in a water solvent with a pH of 4, and the temperature is 30°C;

[0072] Step three, perform pressure filtration and dehydration on the ball-milled lithium residue for 10 times;

[0073] Step four, collect the solution after circulation, and the remaining lithium residue after dehydration;

[0074] Step five, add the collected solution to sodium carbonate and sodium hydroxide, and filter out impurities, and concentrate the filtrate after filtration, to obtain a lithium carbonate filtrate.

[0075] The lithium carbonate solution obtained in the above embodiment is tested for performance, and the results are as follows:

[0076] Table 1 Performance test results of the lithium-rich solution prepared in the embodiment

[0077] Example Lithium ion concentration after enrichment (g / L) Lithium ion concentration after enrichment (g / L) Example 1 0.53 2.65 Example 2 0.59 2.95 Example 3 0.67 3.35 Example 4 0.78 3.9 Example 5 0.85 4.25

[0078] As shown in Table 1, the lithium ion concentration of the solution collected in Examples 1-5 after filtration and concentration is in the range of 2.5-5 g / L, which meets the requirements of lithium carbonate plants for solution recovery, and can be directly used for lithium carbonate purification.

[0079] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for wet extraction of lithium carbonate from lithium slag, characterized in that, The method comprises the following steps: Step one, crushing the lithium residue; Step two, adding water reducing agent and water to the crushed lithium residue for ball milling; Step three, performing cyclic pressure filtration dewatering on the ball-milled lithium residue; Step four, collecting the solution after the cycle and the remaining lithium residue after dewatering; Step five, adding sodium carbonate and sodium hydroxide to the collected solution, filtering out impurities, and concentrating the filtrate to obtain a lithium carbonate filtrate.

2. The method of claim 1, wherein, The water reducing agent added to the lithium residue in step two is a solid polycarboxylic acid type water reducing agent, and the mass accounts for 0.3-0.5% of the mass of the lithium residue.

3. The method of claim 2, wherein, The pH value of the water added to the lithium residue in step two is 2-5, and the ball milling is performed at 10-40℃ for 3-5 min.

4. The method of claim 1, wherein, The concentration of sodium carbonate added in step five is 5%, and the mass percentage is 3%-10%; the concentration of sodium hydroxide added is 5%, and the mass percentage is 1%-3%.

5. The method of claim 4, wherein, In step five, the filtrate after filtering out impurities is concentrated to a lithium ion concentration of 2.5-5 g / L to obtain a lithium-rich filtrate.

6. The method of claim 5, wherein, The filter plate or filter membrane used for filtering out impurities has a pore size of 0.02-2 µm.

7. The method of claim 1, wherein, The lithium residue in the step one is derived from lithium mica and / or lithium spodumene production, and the density of the lithium residue is 1.0-1.2 g / cm 3 , and the specific surface area is 80-200 m 2 / kg.

8. The method of claim 7, wherein, When the lithium residue is derived from lepidolite, the lithium residue needs to be crushed to 200-400 mesh.

9. The method of claim 1, wherein, In step three, the pressure filtration dewatering cycle is 5-10 times.

10. Use of the dewatered remaining lithium residue of claim 1 in the preparation of artificial sand.